/Engine/Source/Developer/MaterialBaking/Public/MaterialBakingHelpers.h
Shrinks the array to a single pixel if the entire output is monochrome. Params will be adjusted accordingly when this occurs. It's useful to perform this before the border smear as a single non-magenta pixel value would have led to a monochrome image post-smear anyway, so the actual smearing process can be skipped.
static void PerformShrinking ( [TArray](API\Runtime\Core\Containers\TArray)< [FColor](API\Runtime\Core\Math\FColor) > & InOutPixels, int32 & OnOutImageWidth, int32 & InOutImageHeight, [FColor](API\Runtime\Core\Math\FColor) BackgroundColor )